BellaOnline Forums Education Astronomy Top Ten Astronomy Stories 2015 *new*

For over twelve years Eris - Dwarf Planet and its moon were the most distant known bodies in the Solar System (except for comets). But late last year - it was announced in November - V774104 was discovered by Scott Sheppard, Chad Trujillo and David Tholin.

V774104 is at 103 AU, which means it's over a hundred times farther from the Sun than Earth is. In earthly distance terms, it's 15.4 billion km / 9.6 billion miles. Astronomers think it's icy object 500-1000 km across, and that it could be part of the Oort Cloud, but they don't currently know anything about it's orbit. That will take at least a year of observation.

The Refsdal Supernova keeps reappearing. The Hubble image shows the past, present and predicted future of the supernova's appearances. The star only blew up once, but the event is being gravitationally lensed by a massive galaxy cluster in front of it. Distant events can not only be magnified by such a lens, but multiplied. The light from the supernova is bent around the cluster so that it reaches us on different paths. They don't all take the same amount of time to get here, so we see more than one image.

The top circle represents 1995, though the supernova wasn't actually observed then. The lowest circle shows the galaxy which lensed the Refsdal Supernova to produce four images — a discovery made in late 2014. The middle circle shows the predicted position of the reappearing supernova. It did reappear there last year.

G is for Gravitational Lens will tell you more about this lensing effect.

Image Credit: NASA, ESA, S. Rodney (John Hopkins University, USA) and the FrontierSN team; T. Treu (University of California Los Angeles, USA), P. Kelly (University of California Berkeley, USA) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

The Refsdal Supernova was named for Norwegian astrophysicist Sjur Refsdal (1935-2009). He did pioneering theoretical work on gravitational lenses in the 1960s, including their effects and possible applications. It had to be theoretical, because the first gravitational lens wasn't discovered until 1979.

In the center of the Hubble image of QSO 0957+561 is what seems to be two very similar quasars, and called the Twin Quasar. Then astronomers realised that these twins are a little too identical - they're close together, at the same distance from us, and have surprisingly similar properties. They're actually two images of the same object which has been gravitationally lensed.

Not many people saw the total solar eclipse in March 2015. The path of totality went over the Faroe Islands and the Svalbard Archipelago. Neither place is densely populated nor usually high on the March tourist agenda. The weather was against observers in the Faroes, but there were still some who saw totality. Cold in Svalbard, but many got a clear sky.

The Astronomy Photographer of the Year 2015 winning photograph was taken by Luc Jamet in Svalbard. Svalbard is about halfway between the northernmost part of Norway and the North Pole.

In the picture, all we see is the Sun's bright corona. A desolate snowy landscape is dark beneath the eclipsed Sun. Yet in the sky you can see where the Moon's shadow ends. Venus is the bright spot in the upper left. One of the judges described it as “otherworldly”.

I was in northern Norway at the time and saw a substantial partial eclipse in a partly cloudy sky. Not as good as a total eclipse, of course, but still a lovely sight.